The intracellular introduction technology of a protein is effective to know characteristics of the protein, and makes it possible for an arbitrary amount of the protein desired to function in cells to remain in cells for an arbitrary period of time. Currently, time signals of expression or modification of a protein engaged in proliferation, differentiation or development of various cells are being clarified. When applying these findings to engineering fields such as regeneration medicine or tissue engineering, by the intracellular introduction technology of a protein, it is expected to broaden various potentialities.
As for such the intracellular introduction technology of a protein, gene trasfer is used today. The gene trasfer is effective when the designated protein in cells is desired to function constantly. However, when the designated protein is desired to function transiently in cells, the method for introducing a protein itself into cells is in use.
Conventionally, as the intracellular introduction technology of a protein, Futami et al., “Biochemistry”, Am Chem. Soc, 2001, Volume 40, Number 25, Pages 7518–7524 discloses a method using a highly cationic protein or a cationized protein by chemical modification.
Schwarze et al., “Science”, Am Ass. For the Advancement of Science, 1999, Volume 285, Number 5433, Pages 1569–1572 discloses a method using a protein added a highly basic TAT peptide derived from HIV.
Futaki et al., “The Journal of Biological Chemistry”, JBC, 2001, Volume 276, Number 8, Pages 5836–5840 discloses a method using a protein added a cationic peptide such as Poly-Arg.
As regards these techniques, it is presumable that the cationized protein, which is the target of introduction, is electrostatically adsorbed on the negatively charged cell surface and is thus taken up by cells with high efficiency. However, these techniques comprising protein cationization require some or other side chain modification of the introduction target protein molecule at a large number of sites, which leads to a decrease in the function of the protein. Further, there is room for contrivance for more easily making it possible for an arbitrary amount of the protein desired to function in cells to remain in cells for an arbitrary period of time so that the properties and the like of the protein may be studied efficiently for the application thereof in regeneration medicine or tissue engineering, for instance.